There is a need to alter or degrade solutions of waste and contaminants. In order to protect and remedy the increasingly polluted ecological sphere while continuing to make industrial and technological progress, it is necessary to provide effective means for altering or degrading chemical and biological wastes. To alter a substance is to chemically change the substance in some way; to degrade a substance is to alter the substance by breaking down the molecular structure thereof.
Trichloroethylene (TCE) is a prevalent chemical waste which has entered the environment at many Environmental Protection Agency (EPA) Superfund sites. These compounds are suspected carcinogens, and, being resistant to aerobic degradation, threaten water supplies.
Conventional techniques used to remedy contaminated sites are fraught with difficulty. Chemical treatment of high volume, contaminated water such as hexane extraction is not cost effective. Air stripping, while lower in cost, merely dilutes the pollutant into the air. Thus, an effective, low cost biological treatment method would be a significant step forward in remediation of contaminated sites. TCE is degraded by a variety of mechanisms. In anaerobic environments, TCE may be converted to more potent carcinogens such as vinyl chloride. TCE biodegradation by aerobic consortia or pure cultures of methanotrophs and pseudomonads has also been reported. Toluene dioxygenase enzyme from pseudomonads has been shown capable of TCE alteration, or degradation. However, either toluene or phenol was required. Other methanotrophic cultures can degrade TCE, apparently by the methane monoxygenase enzyme, without added toluene.
In various studies of biodegradation of a variety of toxic chemicals several problems were apparent. Some of the environments were apparently toxic to the test microbes or the chemicals were adsorbed to the soil particles and not available for degradation by the bacteria. Also, some soils contain extremely small particles, i.e. "fines " which prevent bacteria from penetrating between them and degrading the ensconced chemical(s).
Bacteria used to degrade TCE and other toxic chemicals are currently isolated directly from environmental sources.